Does the Starting battery also need to be wired behind the Victron BMV-602S shunt? - SailNet Community
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post #1 of 13 Old 09-09-2011 Thread Starter
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Question Does the Starting battery also need to be wired behind the Victron BMV-602S shunt?

Hello! Here's another wiring question for you experts...

I'm redoing the wiring on my new-to-me 35 year old boat. Part of that is the battery banks, and part of that is installing a battery monitor. I've settled on the Victron BMV-602S, as it is nicely priced, is apparently easy to install, and does the job it needs to do with a minimum of fuss.

So. It's clear that there can be no loads behind the shunt on the negative battery terminal of the house battery. (By behind I mean, of course, refers to the battery side, not the 'rest-of-the-boat' side).

However, don't I want to connect the negative post on the start bank to the negative post on the house bank? And if so, do I make that connection on the boat side of the shunt or on the house bank side?

In a related question, where does the 'ship ground' go? I assume the 'ship ground' is going to be the engine in most cases, right?

My concern would be that if I connect the ship ground behind the shunt, and then some other piece of electrical equipment also is grounded to the ship ground, then that load would not be monitored by the Battery Monitor, right?

So, to recap, two questions:

1) _If_ I'm supposed to connect the negative side of both banks together, do I connect them ahead of the shunt or behind it?

2) _If_ I'm supposed to connect one or both battery banks to the ship ground (engine?), do I connect them ahead of the shunt or behind it?

Thanks for all the help!

... or I'm wrong.

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post #2 of 13 Old 09-09-2011
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The house bank's negative connection goes to the shunt first. Any connection to any equipment or the engine block is after the shunt. After the shunt I would install a bus for the house negative, start battery negative, and from there go to the block. Do not wire the start battery negative behind the shunt.

Here is a diagram from the manual showing how the start battery is wired with the BMV-602 so it will read voltage of the start battery.
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post #3 of 13 Old 09-09-2011 Thread Starter
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Excellent! That's exactly what I needed... Thanks Brian!

... or I'm wrong.

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post #4 of 13 Old 09-09-2011
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Yes the start battery should go on the "load" side of the shunt not the battery side. If the banks are combined via a parallel switch of BOTH feature you WANT that outflow or inflow of current from the lower or higher charged bank to be read.

When you "combine" banks of different charge levels current flows in or out between them until they "equalize" and the current stops flowing. The only way to read this is to wire the start/reserve battery to the load side of the shunt.

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post #5 of 13 Old 09-09-2011 Thread Starter
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Quote:
Originally Posted by Maine Sail View Post
When you "combine" banks of different charge levels current flows in or out between them until they "equalize" and the current stops flowing. The only way to read this is to wire the start/reserve battery to the load side of the shunt.
Ahh.. that was the part I was missing in my head. Well, that and the diagram from Brian!

... or I'm wrong.

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On the other hand if you use your house bank for house loads and engine starting you can leave the other battery as an "emergency" battery. This battery can be wired to the bus after the shunt and Victron's diagram I posted is the proper way to wire it. The BMV-602 will read the start/emergency battery voltage which is all you need to know. With this exception the data on the Victron relates to the house bank, which is the one you need the info on. There would not be any need to ever combine the battery banks. If the house bank was not enough to start the engine the emergency battery by itself will do the job.

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post #7 of 13 Old 07-12-2012
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Re: Does the Starting battery also need to be wired behind the Victron BMV-602S shunt

Hi,

i am hoping to re-awake this thread.

I have the exact setup as described above with the start battery negative on the load side of the shunt.

All works well except that when the BMV602s back light is off current draw reads 0.00 (that is with all loads and chargers disconnected). If however i scroll through the displays and go back to the current display and now have the back light on it will show a discharge of 1.68 amps.

It is also interesting that if say i am drawing 5.0 amps from the batteries (fridge on) it will show I -5.00 when back light is off and I - 6.68 when back light is on.

I have a feeling it has something to do with the fact that the starter negative is also connected to the shunt.

Any opinions?

Thanks
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post #8 of 13 Old 07-12-2012
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Re: Does the Starting battery also need to be wired behind the Victron BMV-602S shunt

If your starter is connected to the load side of the shunt (and not the battery side) it should make no difference.

If the only difference is the backlight then it is causing the 1.68 amp draw. Seems excessive though.

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post #9 of 13 Old 07-14-2012
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Re: Does the Starting battery also need to be wired behind the Victron BMV-602S shunt

Quote:
Originally Posted by tgalea View Post
If however i scroll through the displays and go back to the current display and now have the back light on it will show a discharge of 1.68 amps.

It is also interesting that if say i am drawing 5.0 amps from the batteries (fridge on) it will show I -5.00 when back light is off and I - 6.68 when back light is on.

I have a feeling it has something to do with the fact that the starter negative is also connected to the shunt.

Any opinions?

Thanks
Tyrone
Sure, your backlight is making this draw (unless you have something else on that we don't or can't know about). I agree with Brian, and it shouldn't have anything to do with the starter negative on the load side. IIRC, it turns itself off on your Victron. On my Link 2000 I have to set its intensity.

Check the manual, IIRC it shows how to reduce it or turn it off. 1.68 ounds high, my Link 2000 uses 0.1 A with backlighting at full.

Have you tried disconnecting the reserve bank and seeing what happens?

Do you haev B1 & B2 connnected right? http://www.victronenergy.com/upload/...e%20-%20EN.pdf

Stu Jackson, C34, 1986, M25 engine, Rocna 10 (22#)

Last edited by Stu Jackson; 07-14-2012 at 08:18 PM.
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post #10 of 13 Old 01-25-2013
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Re: Does the Starting battery also need to be wired behind the Victron BMV-602S shunt

Hi All,

This is the best discussion of the subject on the web, so hopefully I can rewake it once more.

Can someone please let me know whether the charge or current (not voltage!) to/from battery 2 in the diagram from victron energy (in Stu's and Brian's posts, sorry I'm not allowed to post links) is measured at all. I fail to understand how that would work given that current from/to battery 2 can bypass the shunt altogether.

Also, does anyone know whether the shunt can be purchased separately?

Thanks from down under!
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